Fluid flow and heat transfer investigating the hot barrier inside the cavity to form an Islamic knot

This work is based on a numerical simulation to study the flow pattern and heat transfer characteristics inside a cavity in the form of an Islamic knot. The effect of height and length of the obstacle are investigated. Nine different obstacles with different lengths (a) and heights (b) are considered. It can be found that the variation in length and height of the hot obstacle leads to the obvious change in the flow field and temperature field. In addition, the small gap inside the cavity has a limited effect on the flow motion. Besides, the small gap between the cold and hot surfaces leads to higher conduction heat transport. For high Ra, the flow and heat transfer characteristics can be described in two situations. The first is included in the cases of (a,b)=(10,1), (10, 2) and (10, 3), where the primary vortices are located on the top and bottom of the cavity. The second one consists of cases (a,b)=(3,3), (4, 3), (5, 3), (6, 3), (7, 3) and (8, 3), where the primary flow circulations are established on the left and right sides. For all the cases, the average Nu increases by rising the Ra. By increasing the Ra, the average Nu in the second situation increases more significantly than that in the first one. The cases in the second situation always have better heat transfer performance than those in the first one, especially at higher Ra.